Influence of Wire Parameters on Critical Current Versus Strain Characteristics of Bronze Processed ${\hbox {Nb}}_{3}{\hbox {Sn}}$ Superconducting Wires

In order to develop bronze processed Nb 3 Sn wire for the ITER CS coil operating under higher compressive strain, the influence of various parameters of wires such as filament diameter, barrier materials, barrier thickness, heat treatment pattern and Ti addition on critical current (I c ) versus intrinsic strain e ν (-1.0% ν c and n-value. In spite of different wire parameters, the strain dependency of normalized I c was almost the same, except that a Ti addition affects the upper critical field B c2 . This result suggests that assuming the same Ti-addition level, Nb 3 Sn wire with higher performance at a certain e ν would exhibit higher performance at any e ν in the compressive regime. Based on the result, bronze processed Nb 3 Sn wires with non-Cu critical current density more than 1100 A/mm 2 at 12 T, 4.2 K, zero applied strain have been successfully developed for the CS coil.